This is a system and method that broadcasts the radar contacts, visible on a ship-based radar system, over Automatic Identification System (AIS) channels. This system and method allows non-emitting targets to be located and tracked using the AIS system when the targets are near a radar system equipped with this invention. This allows a radar operator to easily share radar contacts with the worldwide community in an inexpensive manner.
Non-emitting targets are hard to track in the ocean because they do not emit radio signals which can be used to detect, locate, and track them. Non-emitting targets close to shore can be tracked using shore-based radar. Non-emitting targets far from shore are challenging to detect because they are out of range of shore-based radar systems. This invention allows radar targets, including targets far from shore, to be rebroadcast to surrounding AIS receivers. These AIS receivers can then receive the information about non-emitting targets at a further range than they could detect with a radar system.
The present invention offers advantages over alternative systems and methods of detecting non-emitting ships. Synthetic aperture radar (SAR) satellites can be used to detect non-emitting ships from space. Some disadvantages of using SAR satellites to detect non-emitting ships include: (1) the expense of satellite imagery; (2) that ship detection algorithms need to be developed; and (3) that the satellites orbit the Earth every few hours and thus don't have the ability to persistently loiter over and monitor a specific area. Another system could be developed that uploads the radar contacts over the Internet using a satellite Internet connection. The disadvantage of such a method however, is the expense of constantly sending data over a satellite Internet connection.